1. Field of the Invention
The present invention relates to a linear solenoid which causes an excitation effect by being energized and a valve device using the same.
2. Description of the Related Art
Conventionally, a linear solenoid valve having a valve element to switch between a communication state and a discommunication state of an inlet port and an outlet port by transmitting a displacement of a movable core caused by an excitation effect of a solenoid has been used.
As for such an linear solenoid valve, the present applicant has proposed a linear solenoid valve which enables an enhancement of an attractive force to a movable core (e.g., see JP 2006-097723 A).
In such a linear solenoid valve disclosed in JP 2006-097723 A, both ends of a shaft passing through a center of the movable core are supported by a first plain bearing and a second plain bearing respectively, and the first and second plain bearings are made of a sintered compact including a sintered metal.
By the way, in the linear solenoid valve disclosed in JP 2006-097723 A, because the shaft is fixed along a center hole passing through the movable core, for example, if an outer diameter of the movable core is reduced so as to achieve a small outer diameter, a saturated state of a magnetic flux density may occur in the movable core. As a result, it becomes difficult to reduce the outer diameter of the movable core, and finally it becomes difficult to miniaturize the solenoid.
Also, in the linear solenoid valve disclosed in JP 2006-097723 A, when the shaft is pushed along the center hole passing through the movable core, an axis of the movable core may moves off an axis of the shaft, and between an outer circumference surface of the movable core and an inner circumference surface of a cylindrical yoke which surrounds the movable core, a force to attract the movable core toward the cylindrical yoke in a radial direction (side force) may be increased. As a result, it becomes difficult to enhance a hysteresis property of the solenoid.
Further, because both ends of the shaft passing through the movable core are supported by the first plain bearing and the second plain bearing respectively, the solenoid is elongated along the axis of the shaft. As a result, it becomes difficult to miniaturize the solenoid.
In addition, associated with the linear solenoid valve disclosed in JP 2006-097723 A, the present applicant has proposed a linear solenoid which can miniaturize the entire device and enhance the hysteresis property, and a valve device using the same (see Japanese Patent Application No. 2009-117052).